refactor: extract shared ESP32-S3 board module

Move common type aliases, peripheral bundles, and init helpers for
ESP32-S3 boards into src/board/esp32s3.rs. Heltec V3 (146->48 lines)
and V4 (155->57 lines) become thin wrappers containing only
board-specific code (Vext GPIO pin, display reset sequence).

Update build.rs to exclude esp32s3.rs from board discovery and
mod.rs.j2 to include the shared module under an ESP feature gate.

src/board/heltec_v3.rs

@@ -1,47 +1,10 @@
+use esp_hal::gpio::{Level, Output, OutputConfig};
+
+use super::esp32s3;
 use super::traits::LoRaBoard;
-use embassy_embedded_hal::shared_bus::asynch::spi::SpiDevice;
-use embassy_sync::blocking_mutex::raw::NoopRawMutex;
-use embassy_time::Delay;
-use esp_hal::dma::{DmaRxBuf, DmaTxBuf};
-use esp_hal::gpio::{Input, InputConfig, Level, Output, OutputConfig, Pull};
-use esp_hal::i2c::master::{Config as I2cConfig, I2c};
-use esp_hal::spi::master::{Config as SpiConfig, Spi, SpiDmaBus};
-use esp_hal::spi::Mode as SpiMode;
-use esp_hal::time::Rate;
-use esp_hal::timer::timg::TimerGroup;
-use static_cell::StaticCell;
 
-use lora_phy::iv::GenericSx126xInterfaceVariant;
-use lora_phy::sx126x::{self, Sx1262, Sx126x};
-
-// ── Concrete peripheral types ────────────────────────────────────────
-
-type SpiBus = SpiDmaBus<'static, esp_hal::Async>;
-type Nss = Output<'static>;
-type Iv = GenericSx126xInterfaceVariant<Output<'static>, Input<'static>>;
-type RadioSpiDevice = SpiDevice<'static, NoopRawMutex, SpiBus, Nss>;
-pub type RadioDriver = Sx126x<RadioSpiDevice, Iv, Sx1262>;
-
-pub type UsbDriver = esp_hal::otg_fs::asynch::Driver<'static>;
-
-pub type DisplayI2c = I2c<'static, esp_hal::Async>;
-
-
-// ── Peripheral bundles ───────────────────────────────────────────────
-
-pub struct RadioParts {
-    pub driver: RadioDriver,
-    pub delay: Delay,
-}
-
-pub struct UsbParts {
-    pub driver: UsbDriver,
-}
-
-pub struct DisplayParts {
-    pub i2c: DisplayI2c,
-    pub mac: [u8; 6],
-}
+#[allow(unused_imports)] // Re-exported for other modules (display, radio, usb tasks)
+pub use super::esp32s3::{DisplayI2c, DisplayParts, RadioDriver, RadioParts, UsbDriver, UsbParts};
 
 // ── Board init ───────────────────────────────────────────────────────
 
@@ -67,78 +30,19 @@ impl Board {
     pub fn into_parts(self) -> (RadioParts, UsbParts, Option<DisplayParts>) {
         let p = self.p;
 
-        // ── esp-rtos scheduler + embassy time driver ──────────────
-        let timg0 = TimerGroup::new(p.TIMG0);
-        esp_rtos::start(timg0.timer0);
+        esp32s3::start_timer(p.TIMG0);
 
-        // ── Vext power: GPIO21, active LOW to enable OLED ──────────
+        // Vext power: GPIO21, active LOW to enable OLED
         let vext = Output::new(p.GPIO21, Level::Low, OutputConfig::default());
         core::mem::forget(vext); // hold pin low permanently; drop would reset it
 
-        // ── SPI + DMA for SX1262 ───────────────────────────────────
-        let spi = Spi::new(
-            p.SPI2,
-            SpiConfig::default()
-                .with_frequency(Rate::from_mhz(1))
-                .with_mode(SpiMode::_0),
-        )
-        .expect("SPI init")
-        .with_sck(p.GPIO9)
-        .with_mosi(p.GPIO10)
-        .with_miso(p.GPIO11)
-        .with_dma(p.DMA_CH0);
-
-        let (rx_buf, rx_desc, tx_buf, tx_desc) = esp_hal::dma_buffers!(256);
-        let dma_rx = DmaRxBuf::new(rx_desc, rx_buf).expect("DMA RX buf");
-        let dma_tx = DmaTxBuf::new(tx_desc, tx_buf).expect("DMA TX buf");
-
-        let spi = spi.with_buffers(dma_rx, dma_tx).into_async();
-
-        static SPI_BUS: StaticCell<embassy_sync::mutex::Mutex<NoopRawMutex, SpiBus>> =
-            StaticCell::new();
-        let spi_bus = SPI_BUS.init(embassy_sync::mutex::Mutex::new(spi));
-
-        let nss = Output::new(p.GPIO8, Level::High, OutputConfig::default());
-        let spi_device = SpiDevice::new(spi_bus, nss);
-
-        // ── SX1262 control pins ────────────────────────────────────
-        let reset = Output::new(p.GPIO12, Level::High, OutputConfig::default());
-        let dio1 = Input::new(p.GPIO14, InputConfig::default().with_pull(Pull::Down));
-        let busy = Input::new(p.GPIO13, InputConfig::default().with_pull(Pull::Down));
-
-        let iv = GenericSx126xInterfaceVariant::new(reset, dio1, busy, None, None).expect("SX1262 interface init");
-
-        let sx_config = sx126x::Config {
-            chip: Sx1262,
-            tcxo_ctrl: Some(sx126x::TcxoCtrlVoltage::Ctrl1V7),
-            use_dcdc: true,
-            rx_boost: false,
-        };
-
-        let radio = RadioParts {
-            driver: Sx126x::new(spi_device, iv, sx_config),
-            delay: Delay,
-        };
-
-        // ── USB OTG CDC-ACM driver ──────────────────────────────
-        let usb_inst = esp_hal::otg_fs::Usb::new(p.USB0, p.GPIO20, p.GPIO19);
-        static EP_OUT_BUF: StaticCell<[u8; 1024]> = StaticCell::new();
-        let ep_out_buf = EP_OUT_BUF.init([0u8; 1024]);
-        let usb = UsbParts {
-            driver: esp_hal::otg_fs::asynch::Driver::new(
-                usb_inst,
-                ep_out_buf,
-                esp_hal::otg_fs::asynch::Config::default(),
-            ),
-        };
-
-        // ── Display (SSD1306 OLED on I2C, 0x3C) ───────────────────
-        let i2c = I2c::new(p.I2C0, I2cConfig::default())
-            .expect("I2C init")
-            .with_sda(p.GPIO17)
-            .with_scl(p.GPIO18)
-            .into_async();
-        let mac = esp_hal::efuse::Efuse::mac_address();
+        let radio = esp32s3::init_radio(
+            p.SPI2, p.DMA_CH0, p.GPIO9, p.GPIO10, p.GPIO11, p.GPIO8, p.GPIO12, p.GPIO14,
+            p.GPIO13,
+        );
+        let usb = esp32s3::init_usb(p.USB0, p.GPIO20, p.GPIO19);
+        let i2c = esp32s3::init_display_i2c(p.I2C0, p.GPIO17, p.GPIO18);
+        let mac = Self::mac_address();
         let display = Some(DisplayParts { i2c, mac });
 
         (radio, usb, display)